1. Technical Field
The present invention relates to a projector which modulates illumination light by using a light modulation device and projects modulated image light.
2. Description of Related Art
A typical known projector includes a light source which emits approximately white light, an illumination system which equalizes light emitted from the light source and converts the light into polarized light, a color separation and light guide system which separates the light having passed the illumination system and guides the light along optical paths for three color lights in green, blue, and red, three liquid crystal light valves illuminated by the illumination lights in three colors, a cross dichroic prism which combines images received from the three liquid crystal light valves, and a projection lens which enlarges the combined image and projects the enlarged image.
When the relative illuminance distributions of lights applied to the respective liquid crystal light valves are different in the projector having the above structure, deterioration of white balance, color unevenness or the like of the projection image obtained by combination of the lights is caused. For overcoming this problem, a method which equalizes the optical path lengths for separated green light and blue light, and inserts a relay lens on the red optical path to correct the illuminance distributions (for example, see JP-A-2005-345604) has been proposed. Also, such a method has been disclosed which sets the number of times of reflection on the respective optical paths at an odd number or an even number such that the respective optical lengths become substantially equal, thereby making the illuminance distributions relatively and substantially equal to one another (for example, see JP-A-8-254678).
According to the projector disclosed in JP-A-2005-345604, however, lights received by the liquid crystal light valves on the blue and green optical paths and light received by the liquid crystal light valve on the red optical path are inverted in the left-right direction, for example. In this case, the illuminance distributions are difficult to be completely corrected. Thus, when the intensity of illumination varies due to fluctuations in light emission point of the light source, shift of component positions within the projector or for other reasons, color unevenness is produced.
According to the projector disclosed in JP-A-2005-345604, the illuminance decreases by complication of optical paths and increase in the number of times of reflection of light even when the illuminance distributions are relatively equalized.